In this dissertation, I show how rhythm became politicized in a number of discourses for example, physiology, psychology, music theory, genetics and eugenics, and aesthetics during the Modernist period, and then focus on its role in the poetry and poetics of W. B. Yeats and Ezra Pound. I argue that each articulates an ideology of rhythm that intersects with the political views within his poetry and generates his celebrated formal innovations. According to these writers, rhythm is a "hidden" ideological effect which can be used by the poet to activate unconscious political energies: both claim that "invisible" or "inaudible" rhythms comprise the political machinery of their poems. Pound describes the science of rhythm as an invisible "strata" (sic) fundamental to the inception of modernism; Yeats discusses rhythm with the same terminology he uses to speak of ghosts. I show that the idea of rhythm as a inaudible and unconscious political force is common in the scientific and aesthetic discourses of the period and assumes prominence in Fascist theories of power. By reading these writers' poetry through their own statements about rhythm as well as through theories of rhythm in other disciplines, I develop a contingent politics of modern rhythm. The formal component of Modernist poetic innovation is, I argue, grounded in theories of rhythm which were themselves overdetermined by ideas of rhythm in the body, in the blood, in the race, in the workplace, and in the body politic. I indicate how theories of rhythm, body and race invited or compelled innovations in poetic form, and argue that such innovations dovetail with what eventually become the authoritarian sympathies of some of the High Moderns. I end with an epilogue examining W. C. Williams' rejection of the term "rhythm" and his development of an alternative sense of "measure." By reading Yeats and Pound as part of a network of extra-poetic texts and ideas, I contribute a chapter to the history of Modernism. I historicize Modernist rhythm in order to theorize the formal choices poets made for their radically innovative work, as well as to bridge the gap between formalist analysis and cultural studies..